The present invention generally relates to a food cooking oven with fan-assisted operation that is adapted to also cook foods by "steaming". More particularly, the present invention relates to an oven which performs the type of cooking that introduces water or steam into the cooking cavity so as to create special food cooking conditions and effects inside said cooking cavity.
In the following description, reference is made in particular to a food cooking oven of the type intended for use in catering operations, professional kitchens, and similar applications. It will, however, be appreciated that what is described and claimed herein actually applies to any kind of food cooking oven that is provided with a forced-convection feature and a "steaming" capability for cooking foods.
It is generally known that, when foodstuffs are cooked in an oven, the related process can be carried out according to different methods and under widely differing conditions, depending on the actual results and effects that one wishes to reach. In this connection, one of the most widely appreciated cooking methods is certainly the so-called steaming process consisting of letting water or steam into the cooking cavity.
This particular cooking method is widely known, so that it shall not be dealt with any farther herein, except for a reference to European patent specifications nos. 0 386 862 (Lechmetall) and 0 183 009, as well as to U.S. Pat. No. 4,856,422, which are incorporated by reference herein and show the actual state of the art.
Systems used to let steam into the cooking cavity of cooking ovens with fan-assisted operation are further widely known to make use of a boiler arrangement located outside the cooking cavity for the generation of steam. A conduit is provided to convey the steam from the boiler into the cavity. In such forced-convection/steaming ovens, the need is particularly felt for appropriate provisions allowing for the flow of the steam being let into the cooking cavity to be regulated in accordance with the actual cooking requirements. As a matter of fact, if such provisions are not available, the corresponding usage of energy (power or gas) by such ovens for generating steam, along with the consumption of cooling water used to possibly bring about (with an appropriate arrangement) condensation of the steam that is generated in excess of the actual needs, is particularly high.
To regulate the flow rate of steam entering the cooking cavity, the provision is generally known of arranging a small-bore tube between the inside of the cooking cavity and the outside of the cooking cavity. The tube is located in an area close to and in front of the axis of rotation of the fan wheel, where a negative pressure with respect to the ambient pressure is created due to the air suction action of the fan wheel. The air and the steam being taken in are pushed by the fan, which is generally of the tangential type, towards the side walls of the cavity and, from there, into appropriate channels flanking the side walls along their whole length and height extension. From the channels, the air and steam are then introduced again in the cooking cavity through appropriate slits or openings.
When a cooking process is being carried out for which steam must be let into the cooking cavity (e.g., steaming or mixed steam and hot air operations), the steam itself condenses onto the food being cooked, so that it transfers heat to the food and causes it to cook. Meanwhile, air at a relatively low temperature (approximately 60.degree. C.) flows in from the conduit which is communicating with the outside.
As the cooking process progresses, there is a gradual decrease in the demand of steam which, when the food is eventually cooked, no longer condenses on the food. Therefore, excess steam creates a slight overpressure inside the cooking cavity and starts to flow out from the tube and, in doing so, contacts a probe provided in the tube. The probe is connected to an appropriately rated and adjusted thermostat nearby which then cuts off the flow of steam towards the cooking cavity.
The steam generator is in this way cycled on and off to perform an intermittent type of operation, with a resulting energy saving effect.
However, the cooking cavity is provided with a fan that is arranged on the rear side of the oven and housed in a back-chamber that is separated from the cooking cavity by a vertical partition wall. Thus, for a correct installation of the steam sensing tube, so as to have its inlet/outlet nozzle appropriately located in front of the suction intake of the fan, two holes must be drilled. That is, a first hole must be drilled in the rear wall of the back-chamber and a second hole must be drilled in the vertical partition wall. The tube is made to run through the holes.
However, the required drilling and assembly operations, as well as the additional operations that must be performed in order to seal the rims of the holes around the tube, must be carried out when the structure of the oven is practically already assembled. Also, these operations are not capable of being automated and therefore bring about an interruption in the working cycle, take up considerable time, and therefore are rather expensive in terms of manufacturing economy.
The main drawback of such an arrangement of the tube, however, is especially apparent in the field, i.e., at the user's facilities. As a matter of fact, it is usually a requirement that the cooking cavity regularly undergo a thorough cleaning operation. To this purpose, the need arises to also gain access into the back-chamber and this, of course, calls for the removal of the partition wall and, along therewith, the tube. Now, this ultimately implies that several assembly and disassembly operations must be carried out each time. These operations, although not very complex, keep a person busy, typically the cook, who is not specifically supposed to perform such technical tasks of equipment maintenance. Furthermore, the subsequent re-assembly of the various parts may be quite easily carried out in a wrong way due precisely to the tube. In addition, the whole cleaning operation requires a significant length of time to be completed.
The need therefore arises to provide a cooking oven, in particular for food service applications in catering establishments, the construction of which does not involve any of the above described assembly and disassembly operations concerning the steam conduit, without requiring any significant design and construction changes.